1. Field of the Invention
The present invention relates to a wide viewing angle polarizer adapted for improvement in viewing angle characteristic of a liquid-crystal display device such as a vertical aligned (VA) liquid-crystal display device.
2. Description of the Related Art
To form a liquid-crystal display device exhibiting excellent display quality in all azimuths by compensation for birefringence of a liquid-crystal cell achieving display through a polarizer, the polarizer needs to be combined with a phase retarder in which main refractive indices nx, ny and nz in three directions, that is, two in-plane directions x and y in association an obliquely viewing direction and one normal direction z, are controlled. Particularly in a VA or OCB liquid-crystal display device, the polarizer needs to be combined with a phase retarder in which the main refractive indices in the three directions satisfy the relation nx>ny>nz.
As the phase retarder with controlled nx, ny and nz used in combination with the polarizer, there is heretofore known a phase retarder made from uniaxially stretched films laminated so that in-plane slow axis directions are perpendicular to each other or a monolayer phase retarder formed from a high-molecular film laterally or biaxially stretched by a tenter. Each of these phase retarders is bonded to a polarizer having a transparent protective layer such as a triacetyl cellulose film through an adhesive layer to thereby form an object.
Use of the former phase retarder, however, brings about a problem that the volume of the phase retarder is large because of use of two retardation films. On the other hand, the range of retardation value obtained in the latter monolayer phase retarder is narrow. In the case where the latter monolayer phase retarder is used and retardation value in the direction of the thickness of the phase retarder is remarkably larger than that in the normal direction, two or more phase retarders need to be laminated in the same manner as the former phase retarder in order to obtain the required retardation value. There arises still the problem that the volume of the phase retarder is large.